Aggressive Driving: Appendix 6
Toward Developing Strategies to Control Aggressive Driving: An Introduction
Richard I. Wark, Roy E. Lucke, Richard A. Raub
Developing a Definition of Aggressive Driving
The term "aggressive driving" has been defined in a variety of ways by researchers and operating agencies. Definitions run the gamut from highly restricted descriptions involving the use of a vehicle as a weapon, to those that include almost every conceivable violation of the motor vehicle code. Confusing media portrayals and political responses to the problem, also make it important to distinguish between "road rage" and "aggressive driving" (Fumento, 1998).
Road rage is best seen as a serious form of criminal behavior employing a car as a weapon or assault arising from driving confrontations. A number of the documented cases of road rage appear to arise from earlier acts of aggressive behavior. As the National Highway Traffic Safety Agency (NHTSA) Web-based publication, Aggressive Driving Enforcement Strategies for Implementing Best Practices (2000) notes:
What is not clear, however, is whether the commonly held assumption that aggressive driving leads to road rage is valid. The literature does not show a clear linkage. In the often quoted AAA Foundation report on aggressive driving (Connell and Joint 1997), the examples used were those of road rage. The final actions were triggered by other incidents not necessarily connected with driving, such as an altercation between two individuals which escalated to the use of vehicles as weapons in their subsequent driving.
The classic concept of aggression identifies it as resulting from frustration (Dollard et al., 1939). This approach provides a theoretical bridge between driver behavior and the driver's environment. For example, to a large extent frustration can be seen as the consequence of the environmental condition of congestion. As congestion worsens, the probability increases that drivers will respond to it by displaying aggressive driving behavior. Other frustrations include work zones and traffic control devices.
However, "aggressive" can have meanings which lead to an understanding of actions based on personality traits more than, or as much as, temporary frustrations. According to Webster's New World Dictionary, 9th ed., one definition of aggressive is "bold and active, pushing." The Oxford English Dictionary, 2nd ed., adds the word "self-assertive." Examples here include motorists failing to yield to merging motorists, and pedestrians walking against "Do Not Walk" signs thereby blocking turning traffic. Perhaps some combination of personality traits, modified by frustrations, may provide a basis for a better understanding of the topic.
Drivers in focus groups held by Northwestern University Center for Public Safety saw aggressive driving as unfair and dangerous to other drivers. This definition may be criticized for being subjective, but programs designed to change behavior should reflect the driver's actual experience. Even if drivers do not verbalize it, they seem to realize that driving is a cooperative venture based on rules. The rules often reflect traffic laws, but not always. Drivers who flagrantly break the rules are perceived as aggressive drivers.
An earlier definition of aggressive driving, which had been adopted by the NHTSA, came from then Secretary of Transportation Rodney Slater: "a combination of unsafe and unlawful driving actions that demonstrate a disregard for safety" (in Goehring 1997, p. 6). Since then, some states have modified it slightly to "when individuals commit a combination of moving traffic offenses so as to endanger other persons or property." This definition, however, ignores the interaction between the aggressive driver and other motorists. Other communities define aggressive driving as the operation of a motor vehicle involving three or more moving violations as part of a single continuous sequence of driving acts, which is likely to endanger any person or property." Here, the definition includes the element of time, as well as other drivers. Finally, NHTSA has modified their definition to read "When individuals commit a combination of moving traffic offenses so as to endanger other persons or property" (Aggressive Driving Enforcement Strategies for Implementing Best Practices 2000).
Depending on how these definitions are applied, may contain the advantage of the subjective definition given above. Clearly, drivers are fairly consistent in what they consider dangerous and are able to deduce intentions. Several states have codified specific traffic offenses, usually in some combination, as "aggressive driving." However, these definitions remains weak because they address safety without addressing other road users. Moreover, they a legalistic approach without recognizing the inter-relationship between the motorist and the driving environment.
In most states, there are sections of the traffic code that defined two other acts that appear to bracket aggressive driving. The first is "Reckless Driving" which is defined as "any person who drives any vehicle in a willful or wanton disregard for the safety of persons or property." The second is "Failure to Yield" which is defined as "Proceeding in a manner …under such circumstances or direction, speed, and proximity as to give rise to danger of collision…." (Uniform Vehicle Code 2000). Aggressing driving should be less than reckless driving, but more than one simple act or failing to yield right of way. The Washington State law classifies aggressive driving under its "Negligent Diving in the Second Degree" (RCW 46.61.525), "operating a motor vehicle in a manner that is both negligent and endangers or is likely to endanger persons or property." For their aggressive driving patrol, the Washington State Patrol has further defined the act as, "The commission of two or more violations that is likely to endanger other persons and property, or any single intentional violation that requires the defensive reaction of another driver" (Field Operations Bureau 2002).
The New York State Police defines an aggressive driver as one who "operates a motor vehicle in a selfish, bold, or pushy manner, without regard for the rights or safety of the other users of the streets and highways" (New York State Department of Motor Vehicles 2000). It is important to maintain the conceptual distinction between aggressive driving and aggressive drivers. These are analytically two different categories, and concentration on one or the other will result in very different types of programs. Emphasis upon aggressive drivers will result in the identification of individuals most likely to drive in an aggressive manner. This could be determined from driving records or clinical data. On the other hand, focus on aggressive driving would lead to programs that are based upon enforcement, engineering, or other environment or educational counter-measures.
Another way of looking at this distinction is to compare the likely goals of these programs. Emphasis on drivers would result in retraining or removing certain drivers from the road. (The clear parallel with attempts to curb impaired driving can be seen.) Emphasis on driving would focus on reducing the frequency and severity of aggressive driving incidents in a given location. Further, the approaches developed for given locations could be generalized and employed on a wider scale, thus affecting the overall instances of aggressive driving.
Finally, at a workshop held in Washington, D.C. November 2000, and from a national survey of traffic safety professionals (law enforcement, public action organizations, administrators, engineers, and educators), a general consensus arose (Raub, Lucke, and Wark, in publication). In this consensus, two themes were important. First, aggressive behavior represents selfish acts often coupled with unsafe driving. Second, the acts had to directly affect other users of the roadway or attempt to disregard traffic controls which have the effect of impeding travel. In this respect, the consensus agreed closely with the definition used by New York. Based on that definition and including the aspect that others must be affected yields a working definition for the proposed Guidebook:
Aggressive driving is operating a motor vehicle in a selfish, pushy, or impatient manner, often unsafe, which directly affects other drivers.
To make this concept operationally measurable, the following specific behaviors were included by the workshop group:
While this list helps to focus on the problem in a practical way, it still has limitations and complications. Some of these behaviors are defined as illegal; whereas, traffic laws do not cover others. As a result, some of the behaviors are not reported or documented in the normal course of traffic law enforcement.
However, as the above list demonstrates, aggressive driving often involves more than violation of traffic laws. For example, attempting to drive at 5 mph over the prevailing speed regardless of the speed limit, and attempting to gain an advantage by flashing lights to "make" others pull aside, does affect others. On the other hand, driving on an non-congested highway at 20 mph over the limit is not aggressive driving when other drivers are not affected "directly," e.g., forced to change lanes to avoid the faster driver. Thus, it may be useful to distinguish between laws and norms. Laws generally have clearly defined limits of behavior which apply regardless of the situation. Norms represent what people interacting in a given situation consider appropriate or acceptable behavior. Norms are important because they allow smooth social interaction to occur. When norms are seriously violated, interaction is disrupted. This would appear to be what happens when behavior that drivers label as aggressive occurs. But this complicates the practical process of identifying the problem and addressing it.
Issues with Programs to Deter Aggressive Driving
Many programs intended to address aggressive driving treat it as any unlawful driving action which endangers others. As a result, a violation such as speeding, regardless of its affect on others, is considered aggressive driving. This premise can lead to counting as aggressive driving citing a speeding driver on an otherwise empty limited-access roadway.
There also is a tendency to assign all crashes for a given causal factor as resulting from aggressive driving. Based on the Fatal Analysis Reporting System (FARS), Dr. Ricardo Martinez in testifying before the US Congress ("Statement" July 17, 1997) stated, "This threat is real. NHTSA estimates that about one_third of traffic crashes and about two_thirds of the resulting fatalities can be attributed to driving behavior commonly associated with aggressive driving (e.g., violations such as improper lane changing, improper passing, red_light running, and speeding)." However, most crash reports, even the more comprehensive ones for FARS will not determine how many of the red-light running crashes, for example, resulted from inattention, fatigue, or a host of other contributing factors not associated with aggressive driving. Another example is that "speed too fast for conditions" becomes speeding. Yet, police officers reporting crashes often will too fast for conditions instead of, for example, "following too closely" because the officer would have to show beyond a reasonable doubt that the vehicles were traveling too close together.
Another problem with addressing aggressive driving only within violations of traffic law is that it provides an easy response, "it is a police problem." Clearly, both the literature and recent efforts by states such as Maryland have shown that substantial police presence coupled with frequent enforcement can reduce crashes. However, the problem is that police generally do not have resources which allow them to continue extensive police patrol.
A final problem is that there is a tendency to relegate correction of aggressive driving only to the law enforcement community. For example, most of what has been released by NHTSA such as one of its most recent guides, Traffic Safety in the New Millennium: Strategies for Law Enforcement, A Planning Guide for Law Enforcement Executives, Administrators and Managers, 2001, concentrates on the legal aspects. The premise is that if a law is passed, the police use the law, the courts uphold it, and the fine is high enough, the problem will be solved. This approach parallels Connecticut's crackdown on speeding where evaluation of the program showed that increasing the penalty, enforcement, and efforts by the court had no effect because of the lack of a clear linkage between the violation, speeding, apparent danger, and the severity of the penalty (Glass 1968).
On the other hand, the results of reviewing driving scenarios by traffic safety experts throughout the country (Raub, Lucke, and Wark, in publication), suggests that equally important is consideration of external elements which affect driving behavior. For example, using the shoulder to reach an exit and avoid congestion is a violation of traffic law, but in some cases the problem may be best resolved by extending the deceleration lane upstream. Traffic law enforcement is important in detecting and intervening at times and locations where aggressive driving is a problem. However, such intervention is not necessarily considered an effective long term solution.
Lajunen, Parker, and Stradling (1998), speak to the importance of distinguishing between aggressive driving violations and other types of offenses. They found that subjects scoring high on a scale assessing anger were more likely to have received violations for offenses classified as aggressive, but not for other types of offenses. This distinction will become increasingly important as researchers attempt to detect patterns of drivers with serious aggressive-driving problems. Driver intention or condition, therefore, becomes a factor in determining whether an action is aggressive. This requires judgment and, in some cases, arbitrary decisions on which types of actions and which specific instances of these actions are to be counted as aggressive driving.
Description of the Problem
The problem of aggressive driving appears to be increasing in seriousness. While there is great variance in the estimates of the problem, perceptions of both law enforcement and drivers are that the phenomenon is becoming more frequent. As a result of this people are experiencing the road as an increasingly dangerous area.
"According to a NHTSA survey on aggressive driving attitudes and behaviors, more than 60 percent of drivers see unsafe driving by others, including speeding, as a major personal threat to themselves and their families. More than half admitted to driving aggressively on occasion. Some common characteristics of the aggressive driver include the following:
A study performed in the U.S. (Connell and Joint 1997) reported incidents of violence that involved traffic altercations and the use of vehicles as weapons. These were only the most violent incidents that resulted in a police crime report or newspaper article. They did represent all the violent incidents that occurred. However, there are attributes of potential interest. In the period January 1, 1990, through September 1, 1996, 10,037 extremely violent incidents reported to a security company conducting the work. The annual count is shown in Exhibit 1. Given the distinction made at the beginning of this paper, these incidents probably would be classified as "road rage."
There is no specific profile for the violent driver. Most are young (18 to 26 years of age), poorly educated males with criminal records, histories of violence, and drug or alcohol problems. Many have recently suffered an emotional or professional setback. However, hundreds of violent drivers are successful men and women with no history of crime, violence, or substance abuse. There were numerous instances where the driver was between the ages of 26 and 50, and 86 reported incidents where the driver was between 50 and 75. According to the study, it seems that a relatively minor traffic event that becomes violent may be the result of a series of stressful events in an individual's life that culminates in extreme violence.
Two related studies were conducted in the United Kingdom and published by the AAA Foundation for Traffic Safety (Connell and Joint 1997). They tended to address the more extreme incidents. While the term "road rage" may be defined differently than it is here, and the driving cultures of the two countries may differ, the limited study of the problem makes these descriptions interesting. They are nicely summarized in a document prepared by the New York State Department of Motor Vehicles (2000).
(One) study was published by the Automobile Association in Great Britain in March 1995. British motorists were surveyed to find out what types of aggressive behavior they had experienced while driving. First they were asked if they felt that motorist behavior had changed in recent years. Of those surveyed, 62% said they felt driver behavior was worse. They were then asked what types of aggressive behaviors they had experienced from other motorists in the last 12 months.
(Twelve percent of the respondents indicated that they had not experienced any aggressive driving behavior.)
(These behaviors may be under-reported here since people may not be willing to admit to some of their more serious actions.)
Most of these incidents happened during daylight hours (70%) on a main road (not freeway or divided highway). Ninety-six percent (96%) of the respondents indicated that their confidence while driving was not affected by the aggressive driving event.
In November of 1996 the AA in Britain published a follow-up to the March 1995 "Road Rage" study. It examined why people experience "road rage" while driving. The study looked at the role of environment in contributing to aggression and compared driving environments to pedestrian environments. Two of the questions raised in this study included:
This study also looked at environmental factors that influence aggression:
Noise-While not provoking aggression, noise has been shown to influence the intensity of a pre-existing case of aggression.
Temperature-In a study conducted in 1986, uncovered a direct relationship between temperature and driver aggression. The hotter it was the more aggressive the subjects became. Most past studies of temperature and its effect on aggression have been inconclusive because if the subject was too hot, they could request that the temperature be adjusted. This perception of control would lessen frustration and aggression. In the 1986 study there was no control of temperature on the part of the subject.
Overcrowding-This is a subjective environmental factor. In experiments where all the subjects agreed that conditions were overcrowded, and especially in the case of traffic congestion, aggression can reach detrimental levels. Noise and heat can exert the most influence on motorists in a traffic congestion situation.
Territoriality-Individuals often view their vehicles as an extension of their home. At home, one sets standards for oneself that may be fine in the privacy of the home but would not be acceptable in public. The car seems to straddle the boundary between private space and public domain."
Because an observable definition of aggressive driving has not been adopted in the United States, it is not possible to document attributes of the problem here in any further detail, such as age, gender, and socio-economic status. Given the clear association between levels of anger and displays of aggressive driving, however, it appears that younger drivers and males would have a higher probability of displaying the behavior. Experience gained from focus groups and driver improvement classes operated by the Center For Public Safety (Wark, 2000) indicate an especially high probability for younger male drivers to express feelings of anger related to driving. Additionally, the enrollment in the driver improvement classes indicates that young male drivers have the highest probability of being ticketed for aggression-related offenses.
The frustration-aggression approach suggested by researchers such as Shinar (1998) has the advantage of allowing for a conceptual relationship between the driving situation and the expression of anger by the individual driver. The basic assumption here is that drivers when exposed to congestion and other frustrating situations will experience increasing levels of aggression. The approach has received much support (see Hauber 1981; McDonald and Wooten 1988; Kenrick and MacFarlane 1986; Underwood 1999; Deffenbacher et al. 1994; and Novaco 1991).
While congestion is not likely to be alleviated in the near future, some efforts have addressed reducing the effects of delay on the motorists. "Frustration over congestion, especially in larger cities, is likely to continue to get worse. People feel the pressure of time and seem to live in the acceleration lane in all aspects of their lives-making every minute count. We believe these feelings on the roadways lead to high risk and aggressive driving, and that, in turn, leads to an increase in crashes" (Aggressive Driving Strategies 2000). Raub and Wark (1998) showed that drivers responded less negatively in a congested situation when they had information about the delay. Much of the effort directed toward incident management also recognizes both the need to reduce the time that driving is interrupted so as to reduce the delay, but also to ensure that adequate and accurate travel information is available to the motorists (see Mannering, Hallenbeck, and Koehne 1992; Hazelkorn, et al. 1996, and Raub, et al. 1996). In addition to adequate information, traffic controls, especially within workzones, need to help ensure the smooth flow of traffic and sufficient information to the motorists (Raub, Sawaya, Schofer, and Ziliaskopoulus 2001).
Another important attribute of the problem is the specific characteristics of the type of driving done by the individual. Ultimately, the likelihood that a given individual will display aggressive driving is a joint probability of their personal characteristics and the characteristics of a particular driving situation. Thus a driving situation could exist that is so non-stressful that it would likely engender aggressive driving only in a person with a great amount of personal anger. Another is so congested and frustrating that even the calmest person could begin to display aggression. The general form of the concept is shown graphically in Exhibit 2.
Aggressive driving is a "contextual" violation. The two major components of context are the driver's state (background and current condition); and the condition of the highway on which the person is traveling. The psychological state of the driver has already been discussed. The driver's background includes experience, both in driving and in society.
The type of aggressive driving displayed in a given area will, in part, also be a function of the setting. Most approaches to aggressive driving have occurred on expressways and perhaps that is why the role of speeding has been emphasized. It is clear that an extension of the concept to driving on surface streets is required. Urban areas with high periodic traffic and heterogeneous mixes of vehicle sizes, pedestrians, and bicycles are especially important to address. In such an environment, the operational definition of aggressive driving would change from something focused upon speed, to violations such as turning, yielding, traffic control devices, and lane maintenance.
Therefore, control will require both detection and correction, both as they are applied to the driver and to the driver's environment. Neither can stand alone. A note addressed to Wark in 2001 from Blatt at NHTSA summarizes the important points (Blatt March 2001):
"It will be important to arrive at an understanding of the underlying phenomena which generate aggressive driving. For, to boldly assume certain factors may miss the opportunity for identifying the most effective approach to the problem.
"Thus…aggressive driving is almost a 'trait' -- a relatively stable characteristic of the individual that is rooted in the individual's social history.
"I expect that these drivers drive more 'assertively' even when there are no other drivers on the road -- driving faster, more rapid speed changes, changing lanes when it suits them, ignoring traffic signs and signals. (These are the same actions that we believe account for the higher incidence of single vehicle crashes of younger male drivers.) These actions become 'aggressive' when other motorists are present and they cause other motorists to take evasive actions (change direction or velocity) to avoid a collision.
"As traffic volume increases, the opportunity for social conflict also increases, thus raising our awareness of these drivers (analogous to the tree falling in the forest) and taking us back to the frustration-aggression hypothesis. Anyone left behind by an aggressive driver is likely to feel somewhat frustrated (and therefore angry) because his legitimate expectation that others abide by the rules of the road has been illegitimately frustrated by the aggressive driver's blatant disregard for others. As a result, the subordinated driver is now likely to exhibit aggressive responses of his own.
"So in addition to the effects of congestion, drivers exhibiting 'trait' aggression can induce 'state' aggression in others."
Objectives for an Aggressive Driving Program
There are two basic objectives for addressing the issue of aggressive driving: preventing drivers from driving aggressively, and minimizing elements of the driving situation and environment that increase the probability of the behavior. These approaches are mutually reinforcing. The first general approach, focusing on drivers, has two basic components:
The second general approach is to examine the driving environment in a search for "triggers" that tend to set off aggressive driving. Efforts aimed at eliminating or reducing traffic congestion guide, are good examples of this approach.
The AAHSTO Strategic Highway Safety Program
One of the hallmarks of the AASHTO program is to approach safety problems in a comprehensive manner. The range of strategies available in the guides will ultimately cover various aspects of the road user, the highway, the vehicle, the environment, and the management system. The guides strongly encourage the user to develop a program to tackle a particular emphasis area from each of these perspectives, in a coordinated manner. To facilitate this, the electronic form of the material uses hypertext linkages to enable seamless integration of various approaches to a given problem. As more guides are developed for other emphasis areas, the extent and usefulness of this form of implementation will become ever more apparent.
The goal is to move away from independent activities of engineers, law enforcement, educators, judges, and other highway-safety specialists. The implementation process outlined in the guides promotes the formation of working groups and alliances that represent all of the elements of the safety system. In so doing, they can draw upon their combined expertise to reach the bottom-line goal of targeted reduction of crashes and fatalities associated with a particular emphasis area.
Discussion of Objectives
Impacting the behavior of populations, or in an area identified as having an aggressive driving problem. The objective here is a general deterrence approach, but in a targeted manner. The targeting of specific age groups is one example. The procedure consists of identifying a series of violations exemplifying the particular problem of aggressive driving in a particular area, or by a specific subset of drivers, and then instituting an intensive program aimed at changing the undesirable behaviors.
Changing the environment to eliminate triggers, or mitigate their effects. This set of strategies targets conditions on the highway that have been identified as causing frustration to the level that aggressive acts of driving are regularly committed. This is a topic about which little is known. Work is needed to determine aspects of the driving environment that increase the probability that such driving will be demonstrated. A generally accepted example of this is the relationship between congestion and aggression, mediated by frustration. Programs of this type would be concerned with the identification and modification of these environmental variables.
Impacting the behavior of drivers with a history of aggressive driving. The target is drivers requiring intervention at the individual level. The objective is to intervene in a way which permanently eliminates aggressive-driving behaviors. Methods of education and behavior modification are needed which enable the habitual offender to learn how to invoke self-disciplines, or create a perception of impending outside imposition of sanctions. In some cases, the behavior modification may occur by systematic application of sanctions. The most appropriate ones would seem to be licensing actions. Treatment of habitual offenders through licensing actions is discussed in detail in the American Association of State Highway and Transportation Officials (AASHTO) Strategic Highway Safety Program (http://safetyplan.tamu.edu) as it applies to unlicenced drivers, or those with suspended or revoked licenses. Similar treatments might be applied here.
Programs aimed at repeat offenders would first require a process for identifying the target persons. While information could be gained from driving records, care would have to be exercised. As noted, aggressive driving is not the same as bad or dangerous driving. Thus, a record containing many moving violations would not necessarily indicate an aggressive driver. The person might drive fast but does so only on roads with minimal congestion, thus not causing problems for other drivers. If violation records were employed, it would have to be done with a classification system that could distinguish between aggressive and non-aggressive violations.
Exhibit 3 summarizes the objectives and associated strategies for their achievement. The strategies will be described separately in Implementation Guide to Address Aggressive Driving.
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Raub, Richard A. and Richard I. Wark. "Response by Motorists to Non-Recurrent Congestion," Paper presented at American Commuter Association Annual Conference, Chicago, IL: September 14-16,1998.
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This paper presents a new procedure for signal coordination along over saturated arterials. It is based on queue management and efficient green time utilization concepts. The main idea is to dynamically manage queue formation and dissipation on system links such that traffic flow is maximized and reason-able through bands are attained. This is achieved by efficiently using green time, preventing intersection blockage, accounting for the non-steady state conditions and providing dynamic, time-dependent control. The problem is formulated as a throughput maximization subject to state and control variables. A solution using Genetic Algorithms (GAs) is then presented. Results show that offsets and green times were dynamically changed as a function of demand and queue lengths. With long queues present, the algorithm utilized appropriate (negative) offsets to reduce or eliminate these queues, and then gradually moved to positive offsets to provide forward green bands, hence normal traffic progression. The algorithm has good potential for on-line real time implementation in an intelligent transportation systems (ITS) environment.
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The purpose of this article is to question the presumption that route guidance and information systems necessarily reduce traffic congestion, and to point out the need to consider the general equilibrium effects of information. A simple model of the morning rush hour is adopted in which commuters choose a departure time and one of two routes to work, the capacities of which are stochastic. While expected travel costs are reduced by perfectly informing all drivers about route capacities, this is not necessarily the case if imperfect information is provided. A heuristic explanation is that, absent tolls, congestion is an uninternalized externality. Information can cause drivers to change the departure times in such a way as to exacerbate congestion.
Chen, Peter Shen-Te, and Hani S. Mahmassani. "Reliability of Real-Time Information Systems for Route Choice Decisions in a Congested Traffic Network: Some Simulation Experiments." Vehicle Navigation & Information Systems Conference Proceedings, Vol. Part 2. 849-55. Dearborn, MI, October 20-23, 1991, no. Part 2. Warrendale, PA. Society of Automotive Engineers, 1991.
This paper investigates the reliability of information on prevailing trip times on the links of a network as a basis for route choice decisions by individual drivers. It considers a type of information strategy where no attempt is made by some central controller or coordinating entity to predict what the travel times on each link would be by the time it is reached by a driver that is presently at a given location. A specially modified model combining traffic simulation and path assignment capabilities is used to analyze the reliability of the real-time information supplied to the drivers. This is accomplished by comparing the supplied travel times (at the link and path levels) to the actual trip times experienced in the network after the information has been given. Results of a series of simulation experiments under recurrent congestion conditions are discussed, illustrating the interactions between information reliability and user response.
Cosijn, D., and P. S. Pretorius. "Transportation Demand Management: One Approach to the Relief of Traffic Congestion." , Vol. 4C. Paper No. 5, no. 4C. Pretoria, South Africa. University of Pretoria, 1995.
Transportation Demand Management (TDM) which in broad terms may be defined as a set of actions aimed at reducing the impact of traffic congestion by influencing the manner in which people travel to work (thereby reducing traffic volumes and vehicle kilometers traveled) is finding favor with numerous transportation authorities world-wide and many success stories are now documented. TDM measures and strategies should be viewed as an integral part of any comprehensive action for the improvement of traffic conditions in our cities.
Daganzo, Carlos F. The Nature of Freeway Gridlock and How to Prevent It. Berkeley, CA: Institute of Transportation Studies, 1995.
This paper presents a continuum model of merge operations and shows how it can be used to describe traffic dynamics on a closed-loop freeway (a "beltway"). The paper shows that it is possible for traffic on a beltway to start a process of self-destruction from which it cannot recover without outside intervention. If allowed to continue indefinitely, the end result of such a process is a gridlocked traffic stream without any motion. A related phenomenon sometimes occurs in roundabouts when priority is given to the entering traffic.
Our result only hinges on three critical assumptions: (i) if a merge is congested, merging vehicles will "force" gaps and trickle into the freeway in a given ratio with freeway vehicles, (ii) vehicles stay on the freeway until they reach their specific destinations, and (iii) when on the freeway, vehicles take up some space that may depend on flow. The paper then describes the collapse process and shows that there is a "relaxation time" or "half-life" during which the freeway flow declines by a factor of ˝. The half-life can be estimated by a simple formula; it can be considerably less than 1 hour for 3-lane freeways. Because speed is very sensitive to flow when flow is reduced from its maximum level, the decline in speed is much more sudden: we estimate that speeds drop by a factor of six during the first half-life. Although a state of complete gridlock should never be reached if there are alternative routes, because drivers would begin to exit before reaching their destinations, the low flows and speeds that would result would still negate the advantage of the beltway over the surface streets. The good news is that the collapse process can be reversed, or better prevented altogether, by restricting the ratio of input flow to mainline flow below a critical level. The paper also identifies such level and describes the recovery process.
Depoy, T. J. "Road Rage Revved Vy Lane Hogs." Roads and Bridges 37, no. 6 (June 1999) 12.
An annual transportation survey of 425 drivers found that Washington-area motorists are overwhelmingly frustrated with slower drivers who stay in the left lane, even those cruising at the posted speed limits. Left-lane crawlers were identified as a leading cause of aggressive driving. Additionally, 46% of the respondents listed aggressive driving as the top safety threat, followed by congestion (20%) and drunken driving (18%).
Dudek, Conrad L., and Gerald L. Ullman. Freeway Corridor Management. Washington, DC: Transportation Research Board, 1992.
Increasing traffic volume and congestion have made it essential to optimize use of existing facilities within urban freeway corridors. Business and service vehicles, as well as people traveling to and from work require around the clock mobility. Managing urban freeway corridors can provide mobility and optimize traffic operations. To do this, a comprehensive strategy is required, consisting of selective roadway construction, transportation demand management actions, and intensive management and control of the roadways in the freeway corridor (including freeways, arterial streets, and high-occupancy vehicle (HOV) facilities). This synthesis addresses the management and control of the entire freeway corridor. The components of a freeway corridor management system include:
Harding, Richard W., and others. "Road Rage and The Epidemiology of Violence: Something Old, Something New." Studies on Crime & Crime Prevention 7, no. 2 (1998) 221-38.
Examines road rage in the context of the general literature on stranger violence and in the context of particular case studies taken from the data base. Empirical data relating to incidents of road rage in Western Australia from 1991 to 1995 are examined. It was found that groups at high risk of violent offending against strangers (young males, Aboriginals) are at less risk of committing road rage violence that street violence and that this is because they are under-represented (or less exposed) as drivers in terms of distance driven; whilst groups at low risk of violent offending against strangers (older males) are more at risk of committing road rage violence than street violence and that this is because they are over-represented (or more exposed) as drivers in terms of distance driven. Yet the dynamics of road rage incidents, when they do occur, conform with general violence analysis as to status defense, identity enhancement and disinhibition. There is thus an old and familiar rage element to road rage; but there is also a new road element brought about by the frustration of over-long exposure to the driving experience. Exposure can bring about an effect where persons who do no otherwise fall within the category of violent offenders can cross that boundary.
Haselkorn, Mark, and Woodrow Barfield. Improving Motorist Information Systems: Towards a User-Based Motorist Information System for the Puget Sound Area. Part 2 . Olympia, WA: Washington State Department of Transportation, 1990.
This report documents new knowledge of Puget Sound freeway commuter behavior and information needs, relevant to the design and development of a motorist information system for the Seattle area. Methodological innovations resulted in a larger, more relevant sample; more complex and varied data; and a finer grain of analysis than previous efforts to survey motorist behavior. Findings are relevant not only to driver information systems in particular, but also to transportation management in general. Commuters were found not to be a single, homogeneous audience for motorist information, but rather to consist of four subgroups, which we labeled: (1) route changers, (2) non-changers, (3) route and time changers, and (4) pre-trip changers. Commuters were more receptive to motorist information delivered at home than to information delivered on the freeway. Most commuters were inflexible about changing transportation mode, but pre-trip changers were somewhat flexible and more likely to change mode than to change route while on the freeway. The most flexible driving decision was the departure time of route and time changers and time changers and pre-trip changers, yet the least flexible driving decision was the departure time of route changers and non-changers. Commuters were fairly flexible to on-road route changes, but less flexible than to changing pre-trip routes based on traffic information received prior to departure. Commercial radio was the preferred medium for on-road traffic information, while HAR and VMS were either not used or not generally perceived as helpful. Whatever the delivery medium, commuters questioned the credibility of motorist information. The report describes how the identification, analysis, and targeting of susceptible driver groups can improve the design of motorist information systems. Recommendations are also presented to improve commuter response to and use of HAR and VMS.
Haselkorn, Mark, Jan Spyridakis, and Woodrow Barfield. "Surveying Commuters to Obtain Functional Requirements for the Design of a Graphic-Based Traffic Information System." Vehicle Navigation & Information Systems Conference Proceedings, Vol. Part 2. 1041-48. Dearborn, MI, October 20-23, 1991, no. Part 2. Warrendale, PA. Society of Automotive Engineers, 1991.
The results of three studies, each designed to obtain functional requirements for the design of a graphics-based traveler information system, are reported. In the first study, the results of a survey are reviewed in which four commuter groups are identified with regard to the impact of traffic information on mode choice, departure time, and alternate route decisions. In the second study, the usability of five prototype traffic information screens are reported. In the last study, the results of a phone interview designed to provide an in-depth understanding of commuter traffic information needs is discussed.
Herman, Robert, Lev A. Malakhoff, and Siamak A. Ardekania. "Trip Time-Stop Time Studies of Extreme Driver Behaviors." Transportation Research Part A 22A, no. 6 (1988) 427-33.
Compared deviations in trip times and stop times for there classes of drivers, "aggressive," "normal," and "conservative." Had each type drive both during peak and off-peak hours in the CBD of several major urban areas. The conservative drive time approached the normal time in off-peak hours. In the peak hours, the aggressive driver approached the normal driving time. However, in all cases, the differences in stop times (and travel times) among the three drivers was significant. The aggressive driver had the least stop time, and the conservative driver the most.
Johnson, Kevin. "Frustration Drives Road Rage." Traffic Safety 97, no. 4 (July 1997) 8-11.
This article focuses on "road rage" which is used to described highly aggressive drivers and driving. However, the article generalizes the commentary to all "aggressive" driving, suggesting that they all are "road rage." It is typical of a number of magazine type articles appearing in the mid-1990's when the media used the alliterative "road rage" to lump all forms of aggressive driving. For example, Cassidy in Traffic World (11 August 1997) states that it "is difficult to distinguish between aggressive driving - which researchers often define as an incident in which a driver purposely attempts to injure or kill another driver or pedestrian - an plain old bad driving." Traffic Safety, School Bus Fleet, Traffic World, Better Roads, and Driver/Education all contain references to aggressive driving and "road rage," and all treat the terms interchangeably.
Joint, Matthew. "Road Rage." Aggressive Driving: Three Studies. AAA Foundation, 17-24. Washington, DC: AAA Foundation for Traffic Safety, 1997.
In its broadest sense, road rage is any display of aggression by a driver, but it is also used to refer to extreme acts, usually some form of assault, arising from operation of a motor vehicle. A survey of motorist behavior (526 drivers) showed that a large percentage of motorists had been tailgated or had lights flashed. These acts were considered "aggressive." However, the circumstances under which these conditions occurred were not determined. Other results of the survey are presented.
Jonah, Brian A. "Sensation Seeking and Risky Driving: A Review and Synthesis of the Literature." Accident Analysis and Prevention 29, no. 5 (1997) 651-65.
The relationship between sensation seeking and risky behavior has been observed since the 1970s. During the late 1980s and early 1990s, road safety researchers have examined the relationship between sensation seeking and risky driving (e.g., driving while impaired, speeding, following too closely), as well as its consequences, e.g., collisions, violations). There is also growing evidence that sensation seeking may also moderate the manner in which drivers respond to other factors such as alcohol impairment and perceived risk. This paper reviews and synthesizes the literature on sensation seeking as a direct influencer of risky driving and its consequences and as a moderator of the influence of other factors. The vast majority of the 40 studies reviewed showed positive relationships between sensation seeking (SS) and risky driving, with correlations in the 0.30-0.40 range, depending on gender and the measure of risky driving and SS employed. Of those studies that have looked at the subscales of Zuckerman's Sensation Seeking Scale, Thrill and Adventure Seeking appears to have the strongest relationship to risky driving. The biological bases of SS is discussed as are the implications for collision prevention measures.
Jovanis, Paul P, and John A. Gregor. "Coordination of Actuated Arterial Traffic Signal Systems." Journal of Transportation Engineering 112, no. 4 (July 1986) 416-32.
Actuated traffic signal installation in a network, while designed to reduce waiting on the lower-volume roads have been shown to increase delays on the arterial street. This work shows that a form of progression can be obtained under an actuated system. However, in studying the differences between a coordinated, fixed-time and coordinated actuated signal system, the fixed time was found to be more efficient than the actuated one, and far more efficient than an uncoordinated activate system. The problem with a fixed-time system is that unless it is made demand sensitive, it also can have significant deficiencies at peak-hour flow.
Kaufman, David E., Smith Robert L., and Karl E. Wunderlich. "An Iterative Routing/Assignment Method for Anticipatory Real-Time Route Guidance." Vehicle Navigation & Information Systems Conference Proceedings, Vol. Part 2. 693-708. Dearborn, MI, October 20-23, 1991, no. Part 2. Warrendale, PA. Society of Automotive Engineers, 1991.
Anticipatory route guidance in traffic networks is based on time-dependent fastest path calculation requiring forecasts of link travel time over a time horizon. These forecasts would be produced by a traffic assignment procedure, which must take into account the behavior of anticipatory vehicles seeking user-optimal route guidance. Thus a conceptual feedback loop occurs. We implement this feedback loop iteratively using simulation for the assignment phase. When the iteration terminates with a fixed-point assignment, user-optimality is achieved. We study the benefits accrued by individual anticipatory vehicles and the system as a whole, as a function of the proportion of vehicles which have anticipatory route guidance., i.e., the market penetration. We observe individual and system benefits at market penetrations up to 40% or higher.
Ledoux, Corinne. "An Urban Traffic Flow Model Integrating Neural Networks." Transportation Research, Part C 5C, no. 5 (October 1997) 287-300.
Adds more depth to the discussion of the value of neural networks for predicting travel time and delays. Agrees that some form of neural network probably will be needed to help ensure adequate real-time travel time projections.
Lomax, Timothy, and others. Quantifying Congestion, Volume 1, Final Report. Washington, DC: National Academy Press, 1997.
The concept of measuring traffic congestion has evolved over the past several decades. At the same time, congestion has "evolved" from a condition afflicting only central cities to a pervasive metropolis-tan problem. NCHRP Project 7-13, Quantifying Congestions, was assigned the task of developing methods to measure congestion on roadway systems. Its goals were to develop methods that are both reliable and understandable: can apply to a route, corridor, or entire region: can relate to simple and easy-to-obtain parameters; and can be forecast. The measures and methods described in this report focus on the needs for congestion and mobility in-formation. This project investigated the range of users and audiences that are associated with congestion and mobility information to determine which measures would best satisfy the range of needs. The measures and data collection procedures center on the use of travel time related procedures. There are also methods to adapt existing volume count and capacity estimation procedures to prepare congestion estimates in appropriate formats.
Lomax, Timothy J., and Herbert S. Levinson. "Overview of Congestion Measurement Principles." Traffic Congestion and Traffic Safety in the 21st Century. Rahim Benekohal eds. 549-55. Chicago, IL, 8-11 June 1997. New York, NY. American Society of Civil Engineers, 1997.
The key to measuring congestion is using travel time and speed measures. They satisfy the widest range of requirements for congestion information. The determination of unacceptable congestion levels is a function of both technical factors and public input. Acceptable travel time and travel rate measures are important concepts that translate the expectations that citizens have for the transportation system into factors that can be used to prioritize transportation system improvements. Other measures such as delay rate, relative delay rate and total delay are useful as measures of performance of system elements. Combining travel time and personal movement will provide a basis for evaluating individual modes and multi-modal transportation systems.
Mizell, Louis. "Aggressive Driving.". Aggressive Driving: Three Studies. AAA Foundation, 1-14. Washington, DC: AAA Foundation for Traffic Safety, 1997.
There have been 10,037 incidents of "aggressive driving" reported in the print media for a 7-year period from 1990 through 1996. These incidents killed 218 persons. The report continues to describe how the incidents took place, who was responsible, the victims, weapons used, and the role of racism and hate. It concludes with how to avoid the "aggressor." Note about the data: given that motor vehicles fatalities average more than 41,000 per year, the deaths from "aggressive driving" represent 8/10ths of one percent of all deaths!
Murno, Michael J., and John S. Pavlovich. "Congestion in Suburbia - A Continuing Challenge." Traffic Congestion and Traffic Safety in the 21st Century. Rahim Benekohal eds. 48-54. Chicago, IL, 8-11 June 1997. New York, NY. American Society of Civil Engineers, 1997.
The unprecedented growth in our cities and suburbs over the last 25 years has outpaced the expansion of the supporting infrastructure. The ability to expand the transportation infrastructure to meet the ever increasing travel demands of the public has been and continues to be a major challenge of the latter part of the 20th century. Compounding the problem are increasing capital costs, decreasing public funds, and community opposition to the expansion of highways through developed corridors. This paper presents a case study of Route 347 in Suffolk County, New York, one of eastern Long Is-land's major transportation corridors connecting the suburban north shore with commercial and industrial centers to the west. It will examine travel behavioral characteristics and transportation habits of the suburban community, development trends over the past 25 years, the transportation philosophies of the municipalities through which it traverses, and the planning process. Additionally, it will discuss such innovative solutions to traffic congestion As: Travel Demand Management (TDM); down zoning; transfer of development rights Telecommuting/Teleshopping; Highway Access Management; and Legislative Solutions as they apply to future development and corridor traffic demand.
Ogden, K. W. "Managing Congestion and Demand - Facing the Challenge." Proceedings, Australian Road Research Board, Vol. part 1. 179-97. Perth, Australia, 9-12 November 1992, no. part 1. Australian Road Research Board, 1992.
This paper discusses the general issue of the management of congestion and demand. It begins by out-lining recent developments in travel demand management (TDM), discussing what can be learned from recent research and experiments. It then discusses travel demand and the factors affecting it now and in the future. The effect of pricing, land use, and transport technology are reviewed for their likely TDM impacts. The paper concludes with some practical conclusions about the role of TDM and its effect on transport planning and policy, including the need to recognize the role of public transport in serving the central city, the limited potential of TDM to affect aggregate travel demand at a regional or metropolitan level, the role of road-building, the key importance of pricing and the moves towards real time road pricing, and the recognition of technological change. In the short term, encouraging increased car occupancy appears to be the most efficacious policy.
Park, Dongjoo, and Laurence R. Rilett. "Spectral Basis Neural Networks for Real-Time Travel Time Forecasting." Journal of Transportation Engineering 125, no. 6 (November/December 1999) 515-23.
In order to provide adequate travel information, there is a need for fast, real-time travel-time forecasting. Current microscopic models are too slow and require too many iterations to match the dynamic travel patterns. Neural networks are being tested. The newer methods also are faster than earlier attempts. However, what successes have been found have been for very short periods, such as for ramp metering.
Pesti, G, P. S. Byrd, D. R. Jessen, and P. T. McCoy. "Traffic Flow Characteristics of the 'Late Merge' Work Zone Control Strategy." Transportation Research Record 1657. 1-9. Washington, DC: Transportation Research Board, (1999).
Conventional traffic control plans such as the one used in Nebraska (NDOR Merge) for lane closures of rural Interstate highways normally work well as long as congestion does not develop. However, when the traffic demand exceeds the capacity of the workzone, queues may extend back past the advance warning signs, often surprising approaching traffic and increasing accident potential. The "Late Merge" is a merge-control concept developed by the Pennsylvania Department of Transportation to reduce the length of queues and reduce the road rage that often develops among drivers, The operational effects of the "Late Merge" were evaluated. The traffic flow characteristics determined from the field data indicate that the "Late Merge" is more effective than the NDOR Merge in terms of the safety and efficiency of merging operations in advance of lane closures on Interstate highways. The "Late Merge" has higher capacity and results in fewer traffic conflicts. However, it was also found that the concept might not be working as effectively as it is capable of. Based on lane distribution data obtained during both free-flow and congested-flow periods, it can be concluded that some motorists did not follow the directions given by the traffic control signs, thus reducing the effectiveness of the merging operation. The potential of the "Late Merge" will not be fully realized until drivers, particularly truck drivers, gain a better understanding and acceptance of the concept.
Raub, Richard A., and Joseph L. Schofer. "Tactics for Enhanced Arterial Incident Management." Traffic Congestion and Traffic Safety in the 21st Century. Rahim Benekohal eds. 277-83. Chicago, IL, 8-11 June 1997. New York, NY. American Society of Civil Engineers, 1997.
Limiting the impact on traffic of non-recurring events such as crashes, traffic stops, or disabled vehicles through effective incident management should be the goal for responders. The arterial incident management study conducted by the Traffic Institute has examined what has been known about how incidents affect traffic and their potential costs, and show how they can be handled to minimize their effects. Important issues addressed included:
Schrank, David L, and Timothy J. Lomax. Urban Roadway Congestion - 1982 to 1994, Volume 2: Methodology and Urbanized Area Data. College Station, TX: Texas Transportation Institute, August 1997.
This research report represents the final year of a 10-year research effort focused on quantifying urban mobility. This study contains the facility information for 50 urban areas throughout the country. The database used: this research contains information on vehicle travel, system length, and urban area characteristics from 1982-1994. Various federal, state, and local agencies provided the information used to update and verify the primary database. The primary database and original source of most of the information is the Federal Highway Administration's Highway Performance Monitoring System (HPMS). Researchers combined vehicle travel and system length data to develop Roadway Congestion Index (RCI) value for 50 urban areas including the seven largest in Texas. The RCI values provide an indicator of the relative mobility level within an urban area.
This report includes an analysis of the cost of congestion using travel delay and increased fuel consumption estimated quantities. The impact of congestion was also estimated by the amount of additional facility capacity required to provide urban mobility. Congestion costs were estimated on an area wide, per eligible driver, a per capita basis.
Spyridakis, Jan, and others. "Designing and Implementing a PC-Based, Graphical, Interactive, Real-Time Advanced Traveler Information System That Meets Commuter Needs." Vehicle Navigation & Information Systems Conference Proceedings, Vol. Part 2. 1045-54. Dearborn, MI, October 20-23, 1991, no. Part 2. Warrendale, PA. Society of Automotive Engineers, 1991.
We discuss the design and implementation of Traffic Reporter, a PC-based, graphical, interactive, real-time, advanced traveler information system created to meet the information needs of Puget Sound area commuters. Traffic Reporter's goal is to influence commuter behavior and decision making so as to improve the efficiency with which commuters use available transportation facilities. This project began by studying commuter behavior and traffic needs in the Puget Sound area. We conducted extensive on-road surveys of Seattle motorists, with smaller, in-depth follow-up surveys. We identified four types of commuters, three of which are likely to respond to various types of traveler in-formation. We then used this understanding of commuter behavior to design and develop a working prototype of Traffic Reporter. This paper describes the design and development of Traffic Reporter, how the current system works, and plans for future development.
Srinivasan, N. S., Arun Herur, and M. Balakrishnan. "Signal Coordination on Urban Arterial Roads - Case Study." Indian Roads Congress Journal 54, no. 3 (November 1993) 601-43.
Coordinated traffic signal systems are needed to reduce driving costs and crashes. Especially important is reducing delay, especially in reducing frequent starting an stopping found in non-coordinated systems. As system introduced, the savings in fuel and travel time are compared to the previous non-coordinated effort. There are significant measurable differences in fuel savings and reduction in travel time. Although lower, the change in crashes is not significant. However, a coordinated system has a large benefit/cost ratio.
Taori, Sunil and Ajay K. Rathi. "Comparison of NETSIM, NETFLO I, and NETFLO II Traffic Simulation Models for Fixed Time and Signal Control -- A Case Study." Transportation Research Record, 1566. 20-30. Washington, DC: Transportation Research Board, (1996).
Use of computer simulations are valuable for decision-making and to supplement tools for evaluating strategies related to traffic management. NETSIM has proven to be the most efficient microscopic model. It produces conservative estimates of traffic flow and speed.
Taylor, M. A. P. "Exploring the Nature of Urban Traffic Congestion: Concepts, Parameters, Theories, and Models." Proceedings, Australian Road Research Board, Vol. part 5. 83-105. Perth, Australia, 9-12 November 1992, no. part 5. Australian Road Research Board, 1992.
Contemporary transport planning is focusing on issues of travel demand management (TDM) for environmental, social and economic reasons. A central part of TDM is concerned with the use of congestion management techniques. This paper considers the nature of traffic congestion and develops parametric descriptions of the levels of congestion in an urban road network. It suggests that there are a variety of manifestations of congestion, which may be grouped into two basic classes: point congestion and network congestion. The use of congestion as a TDM control mechanism is examined, including congestion pricing. The input-storage-output routing equation for interrupted traffic flows is taken as the starting point in the development of a theory of traffic congestion, and for mathematical models that examine the effects of congestion. The paper comprises a review of established theories of the build up of congestion, including Rahmann's storage-output system, the Wardtop-Jewell models of traffic assignment, from which a TDM-modeling strategy can be defined. It considers a set of Para-metric measures of traffic congestion, involving capacity, travel time and delay at the node, link and network levels.
Whitlock, Francis A. Death on the Road, A Study in Social Violence. London: Tavistock Publications, 1972.
Several chapters examine crashes from the perspective of causes, speculations, and criticisms, and the driver. The initial hypothesis is that road violence is one aspect of social violence. The higher the incident of intra-social aggression, the higher the rate of death and injuries on the road. Reference is made to a contest in which two drivers traveled across a city, one obeying all signs and speed regulations, the other driving aggressively. The aggressive driver arrived earlier than the conservative driver, but not substantially earlier. This suggests that aggressive driving does not, in itself, reward the behavior. The author posits that an important factor in aggressive driving arises from frustration with the roadway, traffic, and the conditions under which the driver must perform. Other theories related to aggressive driving are explored and briefly discussed.
Zhang, Hongjun, Stephen G. Ritchie, and Shen-Ping Lo. "Macroscopic Modeling of Freeway Traffic Using an Artificial Neural Network." Transportation Research Record, 1588. Washington, DC: Transportation Research Board, (1997).
This work examines the use of macroscopic modeling for predicting freeway traffic flow in real time. Macroscopic models are much faster than microscopic ones, but they do not provide the precision needed to allow use of predicted traffic flow as a basis for traveler information.